This release does not have a Play Store Description, so we grabbed one from version 1.3-Beta2.1 (1607141901):

Focus is an incredible new kind of gallery, perfectly tuned for speed, efficiency, and ease of use. It features a powerful tagging mechanism to access and organize your albums. All your pictures and videos will be accessible from the main page without the need to change context with an intelligent vertical & horizontal navigation. It's magical.

What does it do?

1 - Tag your photos to keep them organised like never before using a first-of-its-kind
tagging feature - choose from eleven preset tags, or create your own;

2 - Access any image, gif, or video on your device’s storage directly from the main
screen, or dive deeper into your collections to quickly find photos by date;